英语翻译Stability of Slender Webs of Prestressed ConcreteBox-Gir

英语翻译
Stability of Slender Webs of Prestressed Concrete
Box-Girder Bridges
Walter Dilger1 and Alaa Sherif 2
Abstract:Long-span,prestressed concrete,box-girder bridges are haunched and have a span-to-depth ratio of 15 to 20 at the piers.This leads to slender webs,particularly for bridges built with high performance concrete.For girders with sloped webs and constant bottom slab width,the web plate is normally warped,which leads to web curvature in the direction of the principal compressive stresses.It is first shown that buckling is not critical as long as the web is uncracked.But,if the webs have shear cracks,the slenderness ratio of the diagonal compression struts can be very high so that the moments and stability of the curved struts need to be studied.It is shown that the tensile forces in the stirrups—determined according to the truss analogy—will counteract the lateral deformations of the slender compression struts.The procedure,which was developed for the design of the Confederation Bridge in Eastern Canada,will be illustrated by applying it to the slender webs of that bridge.
DOI:10.1061/~ASCE!1084-0702~2003!8:3 138!
CE Database subject headings:Box girders; Concrete,prestressed; Bridges,girder; Webs; Bridges,truss; Stability.
Introduction
For long-span prestressed concrete box-girder bridges,the depth of the webs may reach 12–15 m at a thickness of about 0.40 m.Because haunched box girders sometimes have sloped webs and bottom slabs of constant width,the web plates are not plane but warped.This leads to a slightly curved midplane of the web in the direction of the principal compressive stresses.So,the question arises whether or not these webs are susceptible to buckling,par¬ticularly after the development of shear cracks.After the forma¬tion of diagonal shear cracks the slenderness,klu /r,of the diag¬onal compression struts may exceed the upper limit of 100 for columns ACI 2002!.For this reason,the moment and the stresses developed in these curved struts and their stability need to be investigated.The analysis presented in this paper was developed to check the stability of the slender webs of the 13-km long Con¬federation Bridge that links Prince Edward Island to New Brun¬swick in Eastern Canada.